I've had really good luck with Puget Systems (
https://www.pugetsystems.com/). Not as expensive or slick-looking as StudioCat systems, but they do really solid builds that use proven components. You can choose exactly what you want or seek their advice...all for the just the price of the build. They also stay in touch with you and advise.
They also specialize in REALLY quiet systems, so you can have it in the control room or even in your live room (I only have one room and used to keep my PC in a closet which got really hot. Now it's next to my rack and even my most sensitive mics don't hear it.